The following disclosure relates generally to aircraft landing gears and, more particularly, to aircraft landing gear support assemblies for use with aircraft wings.
Many aircraft have retractable landing gears attached to their wings. These landing gears are generally movable between a static deployed position for supporting the aircraft on the ground and a static retracted position for reducing aerodynamic drag during flight. Because of high landing loads, these landing gears are typically attached to the wings with a very strong support assembly. In addition to being very strong, this support assembly must also accommodate movement of the landing gear between the static deployed and static retracted positions.
FIG. 1 is a partial cutaway top view of an aircraft 100 having a retractable landing gear 112 attached to a wing 108 in accordance with the prior art. The landing gear 112, which is depicted in FIG. 1 in a static retracted position for flight, can pivot downwardly and outwardly about an axis 114 to position a wheel truck 113 for landing. The landing gear 112 is attached to the wing 108 with a landing gear support assembly 110 that includes a forward trunnion support 121 and an aft trunnion support 119. The forward trunnion support 121 is attached to a rear wing spar 106, and the aft trunnion support 119 is attached to a beam 102 extending between the rear wing spar 106 and a fuselage 104. Accordingly, landing loads from the landing gear 112 are transferred to the rear wing spar 106 via the forward trunnion support 121, and to the rear wing spar 106 and the fuselage 104 via the aft trunnion support 119 and the beam 102.
One downside associated with the landing gear support assembly 110 is that the beam 102 must be relatively large, and hence relatively heavy, to transfer the high landing loads from the aft trunnion support 119 to the rear wing spar 106 and the fuselage 104. This additional weight can adversely affect aircraft performance.
FIG. 2 is a top isometric view of another landing gear support assembly 210 configured in accordance with the prior art. FIG. 2 is taken from a perspective looking outboard and slightly forward relative to a rear wing spar 206. The landing gear support assembly 210 includes a forward trunnion support 221 attached to the rear wing spar 206, and a landing gear aft trunnion support beam 215 attached to the rear wing spar 206 outboard of the forward trunnion support 221. The forward trunnion support 221 includes a spherical bearing 222 configured to receive a pin 213 to pivotally support a forward pivot portion 218 of a landing gear main strut 212. The landing gear aft trunnion support beam 215 is at least partially cantilevered from the rear wing spar 206, and includes an aft trunnion support 219. The aft trunnion support 219 is laterally offset from a longitudinal axis 250 of the aft trunnion support beam 215, and is configured to receive a fuse pin 217 to pivotally support an aft pivot portion 216 of the landing gear main strut 212. The term xe2x80x9cfuse pinxe2x80x9d is used herein to denote a cylindrical pin that has been designed to fail under a preselected force.
As best understood by the applicants, the lateral offset between the aft trunnion support 219 and the longitudinal axis 250, in combination with the fuse pin 217 and the spherical bearing 222, enables the landing gear main strut 212 to break free of the aft trunnion support beam 215 and the rear wing spar 206 in the event of an overload condition. As used herein, an xe2x80x9coverloadxe2x80x9d or xe2x80x9coverload conditionxe2x80x9d is defined as a design load condition at which a landing gear support is designed to fail. Breaking free of the aft trunnion support beam 215 and the rear wing spar 206 in this manner apparently prevents the landing gear main strut 212 from causing damage to the rear wing spar 206. This failure mode is desirable because many aircraft carry fuel in their wings directly forward of the rear wing spar and adjacent to the landing gear. Thus, rupturing the rear wing spar in such aircraft could potentially cause a substantial fuel leak.
One shortcoming associated with the landing gear support assembly 210 is that the lateral offset between the aft trunnion support 219 and the longitudinal axis 250 causes the landing gear main strut 212 to put a significant torsional load into the aft trunnion support beam 215 about the longitudinal axis 250 when vertically loaded. As a result, the aft trunnion support beam 215 must be relatively large, and hence relatively heavy, to carry this torsional load without failure. As mentioned above with reference to FIG. 1, this additional weight can adversely affect aircraft performance.
Aspects of the invention are directed to landing gear support assemblies for attaching landing gears to aircraft wings. In one aspect, an aft trunnion support beam for use with an aircraft landing gear support assembly includes a base portion and an aft trunnion support spaced apart from the base portion. The base portion can be configured to be attached at least proximate to a rear wing spar. The aft trunnion support can be configured to pivotally support at least a portion of a landing gear main strut. The aft trunnion support beam can further include a shear center axis extending from the base portion toward the aft trunnion support. The shear center axis can be at least approximately vertically aligned with the aft trunnion support.
In another aspect of the invention, the base portion of the aft trunnion support beam can be attached to the rear wing spar with at least a first breakable element, such as a fuse pin. The first breakable element can be configured to break and release the aft trunnion support beam from the wing spar when the landing gear main strut exerts a preselected force against the aft trunnion support.
In a further aspect of the invention, a method for mounting a landing gear to an aircraft wing includes attaching a forward trunnion support at least proximate to a rear wing spar, and attaching a base portion of an aft trunnion support beam at least proximate to the rear wing spar. The aft trunnion support beam can further include an aft trunnion support spaced apart from the base portion and a shear center axis extending from the base portion toward the aft trunnion support. The shear center axis can be at least approximately vertically aligned with the aft trunnion support. The method can further include pivotally connecting a forward pivot portion of the landing gear main strut to the forward trunnion support and pivotally connecting an aft pivot portion of the landing gear main strut to the aft trunnion support.